1. Field of the Invention
The present invention relates to solvents for soft metals such as lead, copper and related alloys, and more particularly to mixtures that dissolve such metals selectively, permitting removal of such metals from surfaces of steel, nickel and the like.
2. Description of the Prior Art
Often, undesirable deposits of soft metals, such as lead, copper, cadmium, tin, alloys thereof (e.g., solder, a lead-tin alloy) and the like, accumulate on harder metal surfaces such as surfaces of steel, stainless steel, nickel and the like. For example, as bullets or shot pass through the steel barrel of a rifle or other gun, they leave deposits of lead on the bore or interior surface of the barrel. After time and repeated firing of the gun, the deposits accumulate, developing into an increasingly thicker coating of lead on the interior surface of the barrel and leading to decreased shooting accuracy. For bullets jacketed in copper, copper coatings develop on the interior surface of the barrel by the same process. It is therefore necessary to clean the barrel occasionally to remove such coatings.
Other examples of instances in which soft metals must be removed from harder metal substrates include the polishing of brass and the cleaning of soldering surfaces from extraneous solder. With respect to the latter instance, under current practices automobile starters and generators are often burned to melt solder connections to allow recovery of the copper parts for salvage.
A variety of mixtures for dissolving lead and other soft metals are available commercially and have been described in various articles. Solvents for cleaning lead from the barrels of guns are provided by a number of suppliers. Examples of such solvents include Accubore bore cleaner of RTI Research Ltd., Vancouver, British Columbia, Canada, Shiloh Creek bore solvent of Shiloh Creek, Cottleville, Miss., Sweets 7.62 Solvent of L. Sweet, Kingsford, N.S.W., Australia, Proshot Copper Solvent II of Pro-Shot Products, Taylorville Ill., Hoppe's Bench Rest Copper Solvent of Penguin Industries, Inc., Coatesville, Pa., and Shooter's Choice Firearms Bore Cleaner of VENCO Industries, Inc., Chagrin Falls, Ohio.
However, conventional lead solvents typically suffer from a number of drawbacks. For instance, conventional products generally are not as selective as desired in their dissolution of lead, copper or their alloys as opposed to steel. As a result, attempts to remove lead deposit from steel surfaces such as gun barrels lead to undesirable dissolution of a significant portion of the underlying steel surface as well.
Moreover, commercial products marketed for removal of lead or copper fouling from gun barrels generally do not dissolve the lead or copper to be cleaned from the bore, but form an insoluble salt with the lead or copper that must be removed by abrasion, such as with a brass brush.
Accordingly, products and techniques are still needed that allow selective dissolution of the soft metals to allow their easy, nonabrasive removal without serious damage to harder metal substrates.